Two-stroke internal combustion engines have a structure which does not vary substantially with respect to the rotational direction of the engine. The direction of rotation of the engine is largely dictated by the ignition timing signals which must be suitably advanced with respect to the top dead center of the cylinders of the engine.
In some applications of two-stroke internal combustion engines, it is advantageous to enable the operation of the engine in both rotation directions, for example in order to reverse the travel direction of a vehicle.
Of course, it is possible to circumvent this problem by providing a mechanical solution, for example, by mounting a gearbox downstream from the engine's rotatable shaft to determine the direction of travel. This way, the direction of rotation of the combustion engine does not change.
The drawbacks with these mechanical solutions regard the cost and the weight increases caused by the supplementary gearbox.
An electronic solution has also been proposed to allow the direction of rotation of two-stroke internal combustion engines to be reversed. Generally stated, the electronic solution concerns the management of the ignition procedure to cause the reversal of the rotation direction by means of suitable control signals picked up from the voltage generated by the same voltage generator which is powering the electronic ignition system of the engine.
An example of an electronic ignition system allowing the reversal of the rotation direction of a two-stroke internal combustion engine may be found in Canadian Patent Application No. 2,179,351 published on Dec. 22, 1996 and naming Venturoli et al. as inventors. This system uses two angularly spaced signal pickup devices to detect teeth provided on the rotor of the voltage generator. The signals generated by these devices are supplied to a microprocessor. Since the two pickup devices detect the same tooth when the rotor is at different angular positions, the rotation direction of the engine may be deduced by the microprocessor and the signals supplied by the two pickup devices may be used to control the ignition of the engine to keep the direction of rotation or to reverse this direction.
A drawback with the system described by Venturoli et al. is that two signal pickup devices must be provided in the combustion engine and that these two devices must be angularly spaced from one another.